The answers given below are answers that would qualify for full credit. Partial credit was given for answers that were on the right track. Answers are given in red.
Part I: Define the following terms and specify whether they refer to genotype or phenotype. (2 pts each, 8 pts total)
Homozygous - an individual with a homozygous genotype has two copies of the same allele at a particular locus (for example, AA or aa)
Heterozygous - an individual with a heterozygous genotype has two different alleles at a particular locus (for example, Aa)
Recessive - a phenotypic trait associated with an allele (for example, b) that is expressed in homozygotes (bb) but not in heterozygotes (Bb)
Dominant - a phenotypic trait associated with an allele (for example, B) that is expressed in homozygotes (BB) and also in heterozygotes (Bb)
Note: The terms recessive and dominant can also refer to the alleles associated with the phenotype. In the example used above, the allele b would be called a recessive allele and the allele B would be called a dominant allele. Although common in scientific literature, this usage is not encouraged. The terms recessive and dominant are best applied to phenotypic traits rather than alleles.
Part II: Define the term natural selection as used in this course (2 pts)
The change in allele frequency that results when there is phenotypic variation in a population, and some of that variation is due to the genotype influencing the phenotype